Regarding the presentation in the video, it might be good to also explain a bit the difference between a log fall and a human fall, as there are some differences in the forces acting on the safety device. In a fall from 4 meters to the bolt that holds the fall, you need to add about 1 meter for the length of the safety device, so the fall is at least 5 meters. In a fall from 5 meters, the falling body reaches about 36 km/h. Since the log is a rigid body and absorbs no energy, the safety device must absorb all the energy. If the safety device is an endless loop that stretches almost nothing, an almost infinite force acts on it, as it must stop the fall in an instant, which it can't and it breaks. Slightly better is the safety cord if it's dynamic and can stretch. Since it's very short, its stretch is also not sufficient to stop the fall, as the force is still too great. But if we have a modern safety set that stretches 2 meters, the stopping force is reduced enough that it holds. From a rough calculation, we get a speed of 25 m/s, which means a stopping force at 80 kg load of 2000 N or 200 kg, which the human body can withstand. In my opinion, in a similar human fall, the other safety devices wouldn't break either, as the human body, due to its non-rigid construction, would absorb enough energy, which unfortunately would show in a broken spine, internal injuries, tears, dislocated joints, broken neck, etc... In short, a person doesn't survive such a fall with almost static protections. Even modern safety devices don't do miracles and such falls can end with serious injuries.